Taking our headlights off isnt too hard, taking them apart wasnt that bad either. I prefer a map lighter and a screw driver I can have one open in 2 minutes or so. Then black RTV in a tube with a gun and thats it.

I had condensation in on of my headlights a couple years ago, I ended up removing one of the bulbs and sticking my air compressor hose into the light for about twenty minutes to dry it out, then I sealed what I could reach with RTV silicone, didn't pull the light out but I was able to get maybe half of the seams with silicone and never had another problem.

Are you under warranty? That would be my first stop. if not, i would start by taking the headlight in question out and inspecting it for cracks. Could be a crack in the housing or a bad seal attaching the lens to the housing or a loose or hole in the rubber bulb holder.